An organic light emitting display is called a new generation of fantastic display because of its many advantages, such as all-solid-state, active emission, high contrast, ultra thin, low power consumption, wide visual angle, fast response speed, wide operation ranges, easy to realize the flexible display and 3D display. Meanwhile, because the light emitting device has a characteristic of capable of forming a large area of film, which can be used for an ideal large size of a flat panel display apparatus. Currently, the light emitting device widely used is an organic light emitting diode (Organic Light Emitting Diode, OLED). A large size organic light emitting display apparatus made by the OLED, such as the OLED color TV, the OLED flat panel computer, becomes the pursuit of many manufactories currently.
A light emitting device needs a certain driving current to emit light, this driving current is usually provided by a peripheral circuit, for example, a reference voltage source provides a certain voltage VDD to the light emitting device via an active matrix driving circuit of the organic light emitting display panel. As the size of the organic light emitting display apparatus increases, the amount of wiring of the active matrix driving circuit increases, which causes the wiring resistance also increasing, thus a voltage drop generated by the wiring resistance (IR Drop) increases. But IR Drop does not contribute to the light emitting of the light emitting device, instead, it becomes heat power consumption to dissipate, not only reducing the electrical-optical efficiency of the display device, increasing the power consumption, but also affecting the display effect of the display apparatus due to the performance of the light emitting martial of the electrical element will be influenced if the heat in the circuit achieves a certain level.
In the color display technical field, a pixel unit includes three pixels of red pixel, green pixel, and blue pixel. In the existing mainstream technology, in order to simplify the circuit, a light emitting device of the red, green, or blue pixel in a pixel unit is driven by a single voltage source VDD-VSS to emit light. However, due to the preset working voltage of the light emitting device of different color is usually different, for example, the working voltage of the blue light emitting device is higher, and the working voltage of the red and the green light emitting device is lower, which causes the fact that if the supply voltage VDD-VSS applied to the active matrix driving circuit is the same, in order to ensure realizing the white balance display, the matrix driving supply voltage VDD-VSS must be set according to the working voltage of the blue light emitting device. In the case that the blue light emitting device can work normally, due to the preset working voltage of the red and the green light emitting device is lower, in order to make all of the light emitting devices of three colors work normally and form the white balance display according to a proper proportion of strength, the driving transistors set in the active matrix driving circuit needs to substantially share the voltage beyond the range of the preset working voltage of the device. However, for the blue light pixel, the driving transistors in the red and green active matrix driving circuits sharing the excesses voltage and the corresponding power consumption, which does not contribute to the light emitting of the light emitting device, but becomes the heat power consumption to dissipate, which not only reducing the electrical-optical efficiency of the display device, but also affecting the working performance of the light emitting martial of the electronic components due to the heat in the circuit achieves a certain degree, thereby affecting the display effect of the display apparatus.